Arrangement in air blast circuit breakers



Feb. 23, 1954 o w 2,670,420

ARRANGEMENT IN AIR BLAST CIRCUIT BREAKERS Filed Jan. 17, 1950 /m @nfor HFDQKON YORh/QLD Patented Feb. 23,1954

ARRANGEMENT IN AIR BLAST CIRCUIT BREAKERS Haakon Forwald, Valhalla, Sweden, assignor to Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Application January 17, 1950, Serial No. 139,007

Claims priority, application Sweden January 18, 1949 Allmanna Svenska 3 Claims.

In certain known forms of air blast circuit breakers the extinguishing arc is drawn between a pin shaped contact and an annular contact into which the pin shaped contact projects or against which it is forced. For the extinction of the arc, it is very important that the arc shall traverse the opening in the annular contact quite centrally, and in a number of known designs of circuit breakers a separate arcing contact is provided at the opposite side of the annular contact and in alignment with the pin shaped contact, and to this arcing contact the arc may extend from the annular contact. In spite of this precaution, however, the arc has a tendency to burn eccentrically in the annular contact, and the arc does not readily extend between the tip of the pin shaped contact and the tip of the arcing contact.

The present invention relates to an arrangement whereby this disadvantage is entirely avoided and whereby the are from the very beginning is drawn centrally between the tip of the pin shaped contact and the tip of the arcing contact on the opposite side of the annular contact. According to the present invention, this is effected by connecting the arcing contact electrically with the annular contact at all times, and when the pin shaped contact is in contact with the annular contact the tip of said pin contact engages the tip of the arcing contact, and these engaging tips are separated from each other only after the pin shaped contact and the annular contact are separated from each other and the current of air commences to fiow through the annular contact. The are will therefore burn centrally in the annular contact without touching the surface thereof, so that a better extinction of the arc is obtained and damage to the surface of the annular contact by the arc is entirely avoided and the surface of the annular contact that is engaged by the surface of the pin shaped contact is not marred by burning.

The accompanying drawing shows one form of the invention in vertical cross-section.

In the arrangement shown, the annular contact l is formed as an opening in a metal chamber 2. The pin shaped contact 3 is shown in full lines separated from the annular contact I and in dotted lines in contact with said annular contact. The arcing contact 4 is attached to a disc 5 which is in turn connected by means of a flexible conductor 6 with the upper wall of the chamber 2. The disc 5 is also provided with an upwardly projecting pin 1, adapted to slide in a guide sleeve 8 in the upper wall of the chamber.

and a spring 9 tends to force the disc 5 downwardly, so that the arcing contact 4 is in contact with the tip of the pin shaped contact 3 when the latter is in contact with the annular contact I, as when the parts are in the position indicated in dotted lines on the drawing. When compressed air is delivered through the channel I 0, and when the pin contact 3 is separated from the sleeve contact I, an arc is formed between the tip of the pin contact 3 and the tip of the arcing contact 4, and on continued downward motion of the pin contact 3 the compressed air delivered through the channel I0 is distributed around the arc, so that there is no tendency for the arc to move sidewise or eccentrically and it remains in the central position while the disc 5 and the arcing contact 4 are being forced upwardly by the compressed air streaming through the annular contact I.

As the arcing contact 4 is forced downwardly by the spring 9 against the pin contact 3 while the latter contact is being separated from the sleeve contact I, no arc is formed between the pin contact 3 and the annular contact I, since these parts are separated without breaking any current because the contacts 3 and 4 are still in contact with each other, and the sleeve contact I is therefore completely protected from damage by the are.

I claim as my invention:

1. An air blast circuit breaker comprising an annular contact, a pin shaped contact engaging said annular contact, an arcing contact in alignment with said pin shaped contact and located on the opposite side of said annual contact and downstreamwardly of said pin shaped contact with respect to the air flow, means connecting said arcing contact conductively with said annular contact so that such parts have the same potential, and a spring member acting on said arcing contact to force it upstreamwardly against the tip of said pin shaped contact, said arcing contact being actuated by the air blast to move it downstreamwardly out of contact with said pin shaped contact, and said arcing contact being so actuated by air that has already passed through the annular contact.

2. An air blast circuit breaker comprising an annular contact, a pin shaped contact mounted at one side of the annular contact for engaging said annular contact, said contacts being movable in relation to each other, an arcing contact movably mounted in alignment with the said pin shaped contact and located at the opposite side of said annular contact and downstreamwardly of said pin shaped contact with respect to the air flow,

an electrical connection between said arcing contact and said annular contact so that such parts have the same potential and means acting upon said arcing contact to, force it against the adjacent end of said pin shaped contact until the. pin shaped contact and the annular contact have been separated from each other, said arcing contact being actuated by the air blast to reverse the motion of the arcing contact from upstreamward to downstreamward after the pin shaped contact and annular contact have-been. separated from each other, and said arcing contact being: so

actuated by air that has already'passed through the annular contact.

3. An air blast circuit breaker comprising a chamber receiving the air blast, an. annular con.- tact admitting air to said chamber, a pin shaped. contact centrally disposed with respect to the annular contact and located outside said chamber, said contacts being movable relatively to each other, an arcing contact concentrically located with respect to said contacts and normally engaging said :pin shaped contact, and flexible means conductively connecting the arcing contact permanently with said annular contact so that said arcing and annular contacts have the same potential, said arcing contact remaining in contact with the pin shaped contact during the initial. movement separating. the latter from contact with the annular contact, and the arcing contact being separated from the pin shaped contact by fluid pressure after the admission of extinguishing air through the annular contact to said chamber.

HAAKON FORWALD.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,279,536 Thommen Apr. 14, 1942 FOREIGN PATENTS Number Country Date 192,671 Switzerland Nov. 16, 1937 202,338 Switzerland Apr. 1, 1939 214,011 Switzerland July 1, 1941 538,672 Great Britain. Aug. 12, 1941 716,685 Germany Jan. 26,1942 

